1. Field of the Invention
The present invention relates to a cylindrical vibration-damping device used, for example, in a differential mount or a roll mount of a motor vehicle.
2. Description of the Related Art
Conventionally, there has been known a vibration damping device interposed between the members constituting a vibration transmission system to connect the members to each other in a vibration damping manner, one kind of which is the cylindrical vibration-damping device. The cylindrical vibration-damping device, as described in Japanese Unexamined Patent Publication Nos. JP-A-5-126185 and JP-A-11-117973, and U.S. Pat. No. 6,616,130, for example, has a structure where an inner axial member and an outer cylindrical member are arranged to be inserted internally and externally, while the inner axial member and the outer cylindrical member are elastically connected to each other by a main rubber elastic body.
Meanwhile, the cylindrical vibration-damping device is sometimes required to have different vibration damping characteristics in multiple axis-perpendicular directions. Therefore, as shown in JP-A-5-126185, JP-A-11-117973, and U.S. Pat. No. 6,616,130 mentioned above, it is proposed to set a higher spring ratio in the axis-perpendicular directions perpendicular to the main vibration input direction where higher spring characteristics are required by means of forming slits on both sides of the inner axial member.
However, in the cylindrical vibration-damping device having the conventional structure, since the main rubber elastic body is subject to substantially pure compressive force between the opposing faces of the inner axial member and the outer cylindrical member, and what's more, the opposing faces of the inner axial member and the outer cylindrical member are each made to be an inclined plane in an arc shape that quickly varies its inclination angle from the apex to both sides in the circumferential direction, it was hard to fully achieve stiff spring characteristics and excellent durability at the same time. Especially because of the main rubber elastic body subject to substantially pure compressive force, there were some problems in setting the rubber volume large enough and fully maintaining the durability due to the concentration of high stresses at the time of load input coupled with the fact that the opposing faces of the inner axial member and the outer cylindrical member are made inclined in an arc shape in the circumferential direction.
In addition, since the main rubber elastic body is arranged between the opposing faces of the inner axial member and the outer cylindrical member in the main vibration input direction, there was a problem in finding a space for a stopper mechanism that provides a buffer to restrict relative displacement between the inner axial member and the outer cylindrical member between the opposing faces thereof in the main vibration input direction.